This invention relates to a control system for a glow plug of an internal combustion engine, such as a diesel engine.
Diesel engines have glow plugs to preheat the engine combustion chambers before and during engine cranking in order to reliably start the engine. It is desirable that the length of time during which the glow plugs are activated varies as a function of engine operating conditions, such as the temperature of the engine coolant.
In the case where a microcomputer system is used to control the glow plugs in response to the engine operating conditions, the following problem may arise: when the engine starting motor is activated to crank the engine, power supply voltage applied to the microcomputer system may periodically drop below the minimum rating value necessary to operate the microcomputer system, since the power supply voltage is also being applied at that time to the starting motor. These power supply voltage drops generally cause the glow plugs to be inactivated undesirably. In this way, operation of the glow plugs may be unreliable during engine cranking.